The invention relates to a medical device for insertion into a blood vessel through an opening in the wall of said blood vessel, the device comprising a flexible sheet material having a length dimension and a width dimension, the sheet material being foldable in the width direction for placing the sheet material into an insertion configuration and the sheet material being unfoldable to assume a sealing configuration inside the blood vessel for a traumatically contacting the blood vessel wall in a sealing manners the sheet material in the sealing configuration extending along an open contour, partly covering the vessel wall, the device further comprising a gripping element on its outer surface.
From WO 90/14796, an occlusion assembly for sealing puncture openings in blood vessels is described. After puncturing a blood vessel with a needle and introducer sheath and subsequent withdrawal of the needle, the known occlusion device can be inserted into the vessel via the introducer sheath. The known occlusion device comprises a flexible sheet material which is attached to a retaining element such as a thread. In the blood vessel, it unfolds to have a surface area which is larger than the surface area of the puncture opening to be occluded. Subsequently the introducer sheath is removed out of the opening in the vessel and by pulling the retaining thread, the sheet material of the occlusion element will come to lie against the inside of the blood vessel wall. Thereafter, a retainer ring is placed around the thread and engages with the outer surface of the blood vessel for a fixed positioning of the occluding device. The flexible sheet, the thread and the retainer ring are made of bio-absorbable material such that it is ensured that after the opening in the blood vessel has been occluded, these parts will disappear, for example after a few weeks.
It is an object of the present invention to provide a vascular surgery device and method which enables formation of a connection (anastomosis) between a bypass graft and a donor or recipient blood vessel with little or no interruption of the blood flow in the donor or recipient vessel. It is an object of the present invention to provide a vascular surgery device which can be used for instance in coronary bypass surgery, preferably on the beating hart, as well as in peripheral bypass surgery, cerebral bypass surgery and plastic and reconstructive vascular surgery. It is a further object of the present invention to provide a vascular surgery device which can be easily and effectively applied and retrieved with a minimum of trauma to the blood vessel and within a very short period of time, preferably within about one minute.
Thereto the medical device according to the present invention is characterised in that the flexible sheet material in an untensioned state is curved in the width direction. After completion of the anastomosis, the device according to the invention can be easily and reliably retrieved from the recipient vessel as the sheet material is predisposed by its flexibility and its pre-formed curvature to be folded in the width direction upon exertion of a pulling force on the gripping element, directed generally in the length direction of the device. Upon retrieval the sheet material is folded when it is contacted by the sides of the opening in the vessel wall.
The present invention provides an intravascular arteriotomy seal which can be easily inserted into and retrieved from a donor or recipient vessel. During insertion into a recipient artery, occlusion of the artery is required only for a brief moment or is not required at all when intravascular pressure is low. When the seal according to the invention is in place, the blood flow in the opened artery can be resumed and the distal end of the bypass graft can be grafted onto the opening of the recipient vessel without leakage of blood along the seal. Prior to completion of the bonding, such as by tightening (securing) the sutures which connect the bypass graft to the recipient vessel, the sheet material of the device according to the present invention can be withdrawn from the opening in the recipient vessel wherein the device will easily bend in the width direction by contact with the sides of the opening in the vessel wall, due to its flexibility and preformed curvature in the width direction. Thereafter, the sutures can be tightened and the grafting can be completed. With the device according to the present invention only a very short or no occlusion of the blood vessel upon insertion or retrieval is required. Once properly positioned, the seal according to the invention provides a bloodless arteriotomy for precise (microsurgical) anastomosis suturing without interfering with recipient artery blood flow, with minimal damage to the wall of the vessel and without blocking of any side branches in the vessel. The seal according to the invention will be particularly useful for coronary artery bypass grafting on the beating heart, such as for instance described in co-pending patent application WO 97/10753 in the name of the applicant. Because the sheet material of the seal according to the present invention has a preformed curvature in the width direction, the material will have a natural tendency to fold easily in the width direction. Hereby the device can be easily retrieved through the insertion opening by pulling, contrary to the prior art puncture hole occlusion device that is described in WO 97/14796, which is maintained in its unfolded position after insertion into a blood vessel.
Bypass Grafting
To provide adequate blood supply to an organ or tissue with impaired blood supply, the end of an extra vessel (bypass graft) is connected end-to-side or side-to-side to the recipient artery downstream of the obstruction in the recipient artery.
To establish this connection, i.e. the distal anastomosis, blood flow in the recipient artery is interrupted by, for example, temporary ligation or clamping of the artery proximal and distal of the connection site. Once the blood flow is interrupted, the recipient artery is opened (arteriotomy). Next, the exit (distal end) of the bypass graft is connected by suturing (or other bonding method) to the recipient artery. This is achieved by suturing the inside of the bypass graft to the inside of the recipient artery. The rationale of this precise anastomosis suturing is that the inner lining of the vessels (the endothelial layer) is anti-thrombogenic, whereas the outer layer is highly thrombogenic. Thrombosis at the transition of donor to recipient vessel reduces the cross-sectional area of the lumen at the anastomosis and hence jeopardizes the quality of the distal anastomosis. Narrowing (stenosis) of the anastomosis limits the maximum blood flow through the bypass graft.
In a proximal anastomosis, the entrance (proximal end) of the bypass graft needs to be connected to an artery which serves as pressure source of oxygenated blood. If a natural artery can serve as bypass graft, like e.g. the internal mammary artery in coronary artery bypass grafting, only the distal anastomosis needs to be made. Sometimes, however, the internal mammary artery is used as free graft or the radial artery is used as arterial conduit and a proximal anastomosis has to be made. Venous bypass grafts always require a proximal anastomosis, because their transformation to an arterial conduit requires connection to a source of arterial blood. Similar to suturing the distal anastomosis of the bypass graft, suturing the proximal anastomosis requires interruption of the source blood flow in the vicinity of the proximal anastomosis site.
Interruption of Blood Flow in Vascular Surgery: Adverse Effects
Currently, all vascular surgery is performed during interrupted blood flow in the vicinity of the anastomosis, because suturing (or otherwise bonding the vessel edges) requires a bloodless surgical field for proper exposure of the vessel edges. The bloodless field, however, is obtained at a price.
Temporary interruption of blood flow has potentially a number of adverse effects. First, interruption of existing residual flow through a high grade stenosis or, when the artery is proximally totally occluded, interruption of collateral flow to the end-organ may impair its function (ischemic dysfunction). Second, it my jeopardize the end-organ""s cellular integrity (ischemic injury). Third, re-establishment of blood flow after cessation of flow may lead to reperfusion injury and dysfunction. Fourth, during the period of completely interrupted flow, in ischemic tissues noxious metabolites accumulate. The abrupt release into the circulation of accumulated noxious metabolites from the reperfused area may cause adverse effects elsewhere.
Vascular surgeons limit the period of flow interruption as much as possible by performing bypass surgery as fast as possible. This requires (a) a still surgical field, (b) absence of blood which obscures the vessel edges, and (c) experience, concentration and manual dexterity. The distal anastomosis requires meticulous placement of the needle into the edge of the recipient artery entrance (arteriotomy). If the stitch is too close to the edge, there is the risk of wall tissue tearing by the suture wire. If the stitch is too far from the edge, there is the risk of creating a tissue flap in the lumen of the anastomosis with subsequent risk of suture line mural thrombosis and suboptimal anastomosis quality.
The present invention obviates the need to interrupt flow in the recipient artery or limits it to less than about 2 minutes, a period which is not expected to lead to adverse effects.
Coronary Bypass Grafting
Recently, coronary artery bypass grafting on the beating heart has regained interest. Coronary motion can now be restrained adequately with a mechanical stabilization device, as described in WO 97/10753, in the name of applicant. Interruption of the coronary flow, however, in the segment of the recipient artery to be grafted may result in regional myocardial ischemia with ischemic ecg changes, loss of regional contractile function and hence, impaired cardiac pump function. Ischemia may induce conduction disturbances. In addition, inhomogeneous perfusion of the myocardium may create vulnerability to arrhythmias. Changes in rate or rhythm may impair pump function. Reperfusion may cause myocardial cell injury (xe2x80x9creperfusion injuryxe2x80x9d) and induce ventricular fibrillation which causes immediate cessation of all pumping action. However, due to usually well established collateral circulation in patients that require coronary bypass grafting for stable angina, flow interruption for 10-20 minutes is remarkably well tolerated without plasma CPK-MB rise indicative of myocardial cell death. In unstable angina, in contrast, adequate collateral circulation is likely to be absent and coronary flow interruption during emergency coronary surgery on the beating heart may further damage the jeopardized myocardium.
Collateral Coronary Flow
In the normal heart, perforating side branches of the epicardial coronary artery feed the underlying myocardium. In case of a proximal occlusion, there is (limited) flow in these perforating branches, albeit in the reverse direction (collateral flow). The sources of the collateral flow are tiny interconnections with nearby unobstructed branches of the arterial coronary tree. In patients with stable angina pectoris the collateral flow usually has sufficient capacity to provide the flow through the main epicardial conduit needed for the heart during resting conditions. During exercise, however, blood supply becomes insufficient and the patient experiences cardiac ischemia (angina pectoris). Since the lesion progression from flow limiting to totally occlusive atherosclerotic obstruction takes many years, collateral circulation has had ample time to develop by expanding the originally minute interconnections between branches of the coronary tree.
In elective coronary bypass grafting for stable angina owing to a proximal coronary occlusion, the well developed collateral circulation generally allows clamping and isolating of the mid-segment of the coronary artery for creation of the distal bypass connection. However, the consequences of temporary occlusion of the recipient artery proximal and distal of the anastomosis site are unpredictable, because very small arteries cannot be visualized pre-operatively by angiography. Distal clamping of a proximally occluded artery may produce myocardial ischemia in the distal perfusion area, because collateral flow in the epicardial conduit is blocked in the antegrade direction. In addition, clamping or ligating the coronary artery may also block retrograde collateral flow in the epicardial conduit from a more distal side branch to a more proximal side branch which supplies a region which happens to lack adequate collateral flow. Sometimes, the coronary flow interruption is not tolerated and the pumping function of the heart deteriorates. One remedy is to restore the blood flow and convert the procedure to conventional coronary bypass grafting using the heart lung machine. If the coronary artery has already been opened, emergency conversion becomes necessary. Another remedy is to insert an intra-coronary shunt cannula. The present invention prevents ischemic problems and hence, obviates stand-by of the heart lung machine.
Dry Surgical Field
To perform precise coronary bypass surgery, a good view of the arteriotomy edges is required. The presence of blood hampers suturing. Ample collateral flow via perforating branches that happen to be located in the occluded coronary segment produces retrograde flow that wells up in the arteriotomy, obscures its edges and jeopardizes the quality of the anastomosis. The present invention restores the dry surgical field and allows conventional anastomosis suturing without leakage of blood owing to the flexibility of the sealing sheet. In the standard, conventional bypass surgery, the heart is arrested by perfusion of the coronary arteries with, in general, a cold cardioplegic crystalline solution which provides a perfectly clear view on the arteriotomy edges. However, when for example the heart muscle is protected by retrograde blood cardioplegia, the same obscuring effect of blood hampers the anastomosis suturing and the present invention may provide a dry surgical field in spite of the blood cardioplegia. Thus, a useful additional benefit of the temporary luminal arteriotomy seal is the creation of a dry surgical field with unimpaired view on the arteriotomy edges for meticulate anastomosis suturing.
Obstruction to Flow
With the intravascular seal and method of using said seal according to the present invention, which seal may for instance be made of polyurethane of a thickness of about 0.2 mm, a minimal or no decrease in cross-sectional area of the recipient artery lumen is achieved, resulting in a minimal or no obstruction to flow.
Vessel Wall Injury
The major concern with any device inserted in an artery is its potential for wall injury, because intra-arterial injury to the wall may lead to local luminal narrowing due to acute mural thrombosis and/or formation of intimal hyperplasia (scar tissue). As the device according to the present invention will only contact a part of the vessel wall circumference, endothelial damage by the intravascular device of the present invention is minimized. Furthermore, if it has damaged or removed endothelium, re-endothelialization is accelerated owing to the presence of undisturbed endothelium at the opposite side of the arteriotomy. In addition, by only covering a limited part of the inner circumference of the vessel with the seal according to the invention, the entrance to side branches remains open during bypass grafting.
Proximal Anastomosis
One major objective of coronary bypass graft (CABG) surgery on the beating heart is to avoid adverse cerebral effects which occur in 6% of cases. These serious adverse effects are attributed for about 50% to relatively large emboli generated by manipulation of the ascending aorta and for about 50% to relatively small emboli generated by the use of the heart-lung machine, in combination with low arterial pressure.
In the CABG patient, the ascending aorta is usually atherosclerotic as well. Any manipulation of the atherosclerotic ascending aorta may dislodge particulate, atherosclerotic or thrombotic emboli from the aortic wall. These emboli may block the (micro)circulation anywhere in the body, but if an embolus follows the bloodstream to the brain, the consequences may be particularly serious.
In conventional CABG using the heart-lung machine and cardioplegic cardiac arrest, the ascending aorta has to be cross-clamped. Off-pump, beating heart CABG obviates the need to cross-clamp the ascending aorta. Currently, however, virtually all vein grafts are connected at their proximal end to the ascending aorta as source of pressurized oxygenated blood. Each time a side clamp is applied to create a dry surgical field, there is the risk of dislodging particulate emboli.
A slight modification of the earlier described arteriotomy seal according to the present invention, to be used for the distal anastomosis, will obviate the need to apply a side-clamp on the (ascending) aorta for creating the proximal anastomosis of a vein graft or a free arterial graft.
In addition, side-clamping the ascending aorta in an off-pump beating heart CABG patient will locally reduce the cross-sectional luminal area, and hence, will increase resistance to flow. Both the ensuing increased arterial pressure in the ascending aorta proximal to the side-clamp (increased afterload for the left ventricle) and the decreased arterial blood pressure beyond the side-clamp (decreased perfusion pressure for the brain and other tissues) are unwanted side-effects.
Thus, obviating the need for the aortic side-clamp is useful both in off-pump CABG and in conventional CABG using the heart-lung machine.
Conceptually, the sealing device for the proximal anastomosis on the ascending aorta is the same as for the distal anastomosis, but the embodiment is slightly different. First, the hole in the aorta is not created by a longitudinal incision, but by punching a round hole (3-4 mm in diameter). Second, the dimensions of the seal conform to the ascending aorta with an internal diameter 25-30 mm and wall thickness 15 mm. Thus, the umbilical cord/inflation channel cannula inserts in the middle of the seal. Fourth, the seal is oval or round. Fifth, the inflatable embodiment may be a torus as well (xe2x80x9cdough-nutxe2x80x9d).
Method. After punching the hole, the sealing device is inserted in the hole (and inflated). Traction on the umbilical cord/inflation cannula may be needed to obtain proper sealing without leakage.
Similar to the distal anastomosis, the aortic sealing device effectively seals the punch hole and permits conventional anastomosis suturing owing to the seal giving way to the needle with little or no leakage. Little leakage will pose no problem, because a clear field is easily obtained by flushing with saline. Similar to the distal anastomosis, the seal is deflated and retrieved after all stitches have been placed but prior to tightening the running suture. The umbilical cord/inflation cannula has a stopping plate or ring/syringe connector to prevent loosing the sealing device within the aorta.
The intravascular seal according to the present invention comprises in one embodiment a relatively short gripping device on the outer surface thereof. The gripping device may be formed by a notch, placed at a specific angle with respect to the outer surface of the seal. With the notch, which may for instance be of a thickness of 0.5 mm and of a height of about 1 mm, the seal can be manipulated during insertion for positioning the seal correctly inside the vessel, and during retrieval.
For properly orienting the seal, an upstanding ridge can be provided on the outer surface within the boundary of the arteriotomy such that the seal may be rotated inside the vessel. Orientation markings, for instance a grid structure may be applied on the outer surface for proper positioning. To minimize the risk of spontaneous inadvertent expulsion of the seal, the stiffness of the flexible sheet material can be greater in the length direction than in the width direction, for example by a midline thickening (longitudinal ridge at luminal side of flexible sheet).
A further embodiment of the device according to the present invention comprises an inflatable body, for instance two membranes that are sealingly connected along their perimeter and a supply duct for supply of a fluid into the space between the membranes for inflating and deflating the sealing device. The luminal membrane is made of a stiffer material to keep the space between both membranes exceedingly small. In this way, the expansion of the device in the width direction can take place by inflation. By deflating the seal, and for instance creating a slight vacuum inside, the dimensions of the seal can be reduced significantly for easy insertion into and retrieval from the vessel.
In another embodiment of the arteriotomy seal according to the invention, the gripping element is formed by a supply duct which ends in an opening in the flexible sheet material for administration of substances through the supply duct into the recipient blood vessel. This device is particularly suitable for instance for performing a rescue blood perfusion during emergency coronary bypass grafting. The rescue blood perfusion pressure should not exceed normal intra-coronary pressure in order to avoid inadvertent expulsion of the device. The perfusion seal may be used in a non-rescue situation when contractile function of the distal myocardium is marginal.
As the seal according to the present invention is retrieved from the vessel the material is non biodegradable which allows for a large choice of suitable, non biodegradable materials such as for instance a polyurethane material, or other materials from which commercially available balloon catheters are manufactured such as available from Medtronic, Minn., USA; Research Medical Vascular, Research Medical, Inc. Midvale, Utah, USA.
The seal according to the present invention was evaluated in a porcine carotid artery (internal diameter 3.5 mm) bypass graft model. In 16 consecutive pigs (32 anastomoses), the seal insertion time was about 20 seconds. The retrieval time was about 5 seconds. Together with the time required for making the arteriotomy and securing the running suture, respectively, median occlusion time upon insertion or retrieval was about 90 seconds. Microsurgical suturing was performed without leakage of the seal and with unimpeded flow. Throughout the anastomosis, no more than one third of the inner circumference of the recipient artery at the anastomosis showed absence of endothelial cells after two days. No medial necrosis was observed. After four weeks, intimal hyperplasia at the sutureline was not significantly different from conventionally sutured anastomoses.
Application of the seal during left internal mammary artery bypass grafting to the left anterior descending coronary artery (internal diameter, 2 mm) on the beating heart was successful in the first 7 additional pigs.